Time-motion analysis in men’s breaking: A longitudinal study

Quantifying the effort of a sport confrontation by determining its temporal structure is of concern to the scientific community. In breaking this has not yet been sufficiently studied. The objectives of the study were to longitudinally analyze the temporal and sequential parameters of male breaking battles to determine the evolution of these parameters and to establish a model of temporal structure. All Red Bull BC One dancers from 2011 to 2021 (n = 152 dancers) participated. By using observational methodology, all battles were analyzed (n = 142). To obtain the results, we employed different analysis techniques: descriptive, normality tests, Student’s t-test or Mann-Whitney, one factor ANOVA or Kruskall-Wallis and effect size (Cohen’s d or Hedges’ g). The significance level established for the study was ρ ≤ 0.05. The results define the temporal and sequential structure of the battles. With these, breaking professionals will be able to develop precise and adequate training for these athletes. We conclude that approaches to dancing and battling have evolved. The effort that the athlete must exert is increasing and will therefore require better preparation to cope with the physical demands required for a sport that will be incorporated into the Olympics program in 2024.


Introduction
All sports involve an internal technical-tactical logic that determines the effort that athletes have to make [1].In some sports the effort is continuous (cycling, swimming, etc.) and in others the effort is intermittent (boxing, soccer, dance, etc.).In terms of the latter, there are also disciplines in which the intermittency and duration of the effort is dictated by the rules due to mandatory breaks (e.g.boxing), and others where the existing breaks are of an uncertain number and duration owing to their internal logic (e.g.judo).In breaking, effort and rest are of an indeterminate duration.While one performer intervenes (makes the effort), the other rests (pauses) before the roles are switched.The period of time in which the dancer makes effort equals the opponent's pause time.
The pauses and actions performed by the athletes condition the type of effort to be made.In turn, this determines the most appropriate training structure and load for the athlete.Each

Participants
Participants were all dancers (n = 152 dancers) who competed in 10 Red Bull BC One world championships (2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020)(2021).The inclusion criterion is that all championship battles had three rounds.The 2014 championship was excluded because of its competition system, which involved a changing and inconsistent number of rounds.In the 2020 championship, for reasons related to Covid-19, the participants were reduced to eight instead of 16.In total, 142 battles were analyzed.The video material was obtained secondarily (from the official Red Bull BC One YouTube channel) and the data were not generated by experimentation, which is why informed consent from the participants was not required [18].The study was approved by the Ethics Committee of the Faculty of Education and Sport Science (University of Vigo, Application 02/0320).

Instruments
The ad hoc observation instrument developed for the research consists of a series of categories that allowed the behaviors performed by the dancers during the battles to be analyzed.The instrument described in Table 1 is an exhaustive and mutually exclusive category system [16] called an Observed Temporal System for Breaking v2 (OTSB v2), this being a revision of the first version used in a pilot study [1].
After designing and testing the observation instrument, construct validity was assessed by means of its consistency with the theoretical framework [19] and by consulting three experts in breaking.The experts were required to show their degree of agreement with the instrument, reaching an agreement level of 95%.The data were recorded using LINCE PLUS software [20].

Procedure
After adequate training in the use of the instruments, the data from the battles were observed and recorded with LINCE PLUS software by two expert observers.To ensure rigor in the recording process [21], the quality of the recorded data was controlled by calculating intraand inter-observer agreement using Cohen's Kappa coefficient [22], calculated using LINCE PLUS software.In both cases, the calculation of the kappa coefficient was applied to all the categorical variables of the observation instrument, obtaining the mean value of all of them.Both concordances were carried out with non-matched subjects who did not belong to the final sample, in a number equivalent to one third of the final sample (n = 50).First, intra-observer agreement was performed, obtaining a mean kappa value for all categories of 0.96 in observer 1 and 0.91 in observer 2. Subsequently, inter-observer agreement was calculated, obtaining a mean kappa value for all categories of 0.90.
All battles were observed.The men's battles comprise six rounds (three per dancer).Each athlete was studied individually, recording the movements they executed and their duration.

Category
Subcategory Code Description TOPROCK TR It encompasses any movement executed while standing in order to keep up with the rhythm of the music or the beats that the song marks.It usually marks the beginning of a round.

DOWNROCK Drop
D Short transition that involves changing from toprock to another move (usually inside downrock).It is used to reach the floor in an original way.Usually follows the beat.

Footwork
FW Movements done on the floor using feet and hands as support.It can follow the beat directly or not and has multiple levels and approaches.It is not essential to be constantly touching the floor with an extremity.Floorrock would be one of the common levels of footwork, movements that are in direct contact with the floor, on the back, chest, shoulders, etc.

S
Every spin with a minimum of 360 degrees while on the floor is considered a spin.When the breaker spins several times in the same move, it becomes part of the family of powermoves.
Powermove PM Explosive and complex set of fine movements using centrifugal power and dynamic balance.They have more than one axis of action (sagittal, longitudinal and transversal) and often lead to a circle.All those movements of 1 to 4 support have the possibility of an aerial phase and a reception while moving.They can follow the beat or not and they can be linked in combos that we will register as several powermoves in a row.

BU
Combinations of fast and unexpected movements that have surprise within the set of the dancer.They can contain freezes, powermoves or flips.

AC
It includes all movements in which there is no contact with the floor and has a well-defined aerial phase.Flips and gymnastic stunts as strict definition.It can follow the beat or not.

Transition T
The main function of these movements is the link between different categories.It depends on the imagination of the dancer and adds originality and creativity to the round.

F
Poses in which the dancer stops moving completely in the middle of a set.It provides control and pace to a dancer´s round.Inside the freezes, there can be tricks or combos that we register as several freezes in a row.They can follow the beat or not. https://doi.org/10.1371/journal.pone.0293131.t001 After all the battles were recorded, we obtained an Excel file with the sequentiality and temporality of all the study behaviors.The versatility of this file allowed us to perform successive transformations for the different analyses.After obtaining the results, we made a model of the temporal structure of the battle.This model was made by consensus by a breaking expert and an expert in time-motion with ample experience in the construction of other temporal structure models [1]. .These mean values were also compared between the different phases of the competition and between the different rounds by means of a one-factor ANOVA (applying a post hoc Tukey-b test in the case of statistically significant differences) when the sample was normal or by means of the Kruskall-Wallis test when the sample was non-normal.The significance level was considered to be p<0.05.We analyzed the effect size by Cohen's d when the sample was normal and by Hedges' g when the sample was non-normal, considering the following values to determine the effect size: d or g < 0.2 (null), d or g = 0.2-0.49(small), d or g = 0.5-0.80 (moderate) and d or g > 0.8 (large).

Analysis of the battles: Totality of the competitions, competitive periods and phases of the competition
Table 2 presents a descriptive analysis of the sequential and temporal parameters of the male battles in the totality of the competitions and in two competitive periods and a comparison between them both.Significant differences (effect size in parentheses) were observed between the two competitive periods in several global temporal parameters.The values are higher in the second competitive period for battle time (moderate), toprock time (small), drop time (moderate) and footwork time (moderate).And higher in the first competitive period in terms of transition time (small).Regarding the sequential parameters, we see greater use of toprocks (large), drops (small), footwork (moderate) and blowups (small) in the latter years and a higher use of transitions (small) in the former.Furthermore, the average time of an element had a small increase in the second competitive period.
Table 3 shows an analysis of the battles according to the phases of the competition (top 16, top 8, semi-final and final).The only differences are in terms of the total number of footwork elements.

Analysis of battle rounds: Overall championships (2011-2021), first competitive period (2011-2016), second competitive period (2017-2021) and comparison between competitive periods (2011-2016 vs 2017-2021)
Table 4 presents a description of the temporal and sequential parameters of each of the battle rounds and a comparison between them in the totality of the championships.We found significant differences in the total round times, toprocks, drops and powermoves, in the total  number of elements per round, in the total number of drops, powermoves, acrobatic elements and transitions, and in the average time of an element and a toprock.It should be noted that each dancer does not appear in all six rounds but in three, alternating between question (first dancer) and answer (second dancer).Table 5 describes the temporal and sequential parameters of each of the battle rounds in the first competitive period, comparing them with one another.We found significant differences in the total round times, toprocks and powermoves, in the total number of elements per round, in the total number of spins and powermoves and in the average time of an element and a toprock.
In Table 6 we analyze the second competitive period.There are significant differences between the rounds in total round time and toprock and powermove time, in the total number of elements per round, the total number of drops, powermoves and transitions and the average time of a spin.
In Table 7 we show a comparison of the rounds between both competitive periods in order to examine their evolution in terms of competing.Differences were found in the following categories: total time of rounds, toprocks, drops, footworks, spins, transitions and freezes and the average time of an element, footwork, a blowup and a transition.

Discussion of the results
Regarding the results of this study, we would like to highlight that the average time of a battle is 182 s.Battles are short but concentrate a great deal of effort and wear and tear in short  periods of time, similar to climbing, gymnastics or certain martial arts [1, 14,23].Battle time is superior in the second competitive period.The difference between 172 s and 193 s may seem irrelevant, but in a confrontation it can mean more information and greater intensity or cardiovascular wear and tear that can have a negative impact on following rounds and make the difference between victory and defeat [1, 14,24].This change, together with the increase in toprocks, drops and footwork, both temporarily and sequentially, indicates that breaking is  focusing more on elements that bring aesthetics and content to a battle, without seeking an insubstantial increase in its duration.We consider that the categories that have not presented a noticeable change are also important, since their neutrality indicates the relevance and permanence of the physical pillar, as is the case of the powermove [1].
Therefore, our results confirm the stability of the physical part of breaking, especially the powermove [1], and the importance attached to aesthetics and fluidity, which concurs with the judging system to be used in the Olympics, the Trivium [8,10,[25][26][27].
The analysis of the battles according to the competitive phase shows that footwork is more prevalent in the final, as is the case with most categories.This is because the final concentrates the most information (and sometimes the most powerful information).Footwork is most likely a type of wild card used to highlight the final movements of the artist.It comes as no surprise that this element is the most recurrent in the final, since it is the core of breaking [1, 24,28].The rest of the categories remain neutral without abrupt changes between rounds, showing consistency in the basic structure of the confrontations.
Our results show the overall behavior of the rounds throughout the 2011-2021 period.We can see that the time of the round, toprocks, drops and powermoves decrease as the battle progresses, with the highest values in the first two rounds and small peaks in the final two rounds.This is because producing a strong finish is key to capturing the judges' attention.The first and last rounds are therefore the most important so the dancer can start and finish in a forceful way [24].Consequently, the powermove is most frequent in the first two and final two rounds.The toprock does not show strong variations compared to other categories.This could be due to the fact that, in the 30-40 s that the round lasts [1], this element provides volume, without demanding too much energy, allowing a few moments of active recovery before returning to the ground.
For the first two rounds we observed a higher frequency of elements with peaks in the final two.The sequentiality and frequency of the elements may be influenced by the opponent, since what one dancer does directly or indirectly affects the other.It should be noted that elements can adapt to the movements of the opponent [24,28,29].Contrary to popular opinion, we found that acrobatics are rarely used in a round.Moreover, they are more frequent in initial rounds than in closing ones, perhaps owing to the fact that these movements require very high amounts of energy and concentration and there is a high risk of making mistakes that alter the development of the battle, as is the case with the powermove [1,14].
We found that in the final two rounds the elements have a longer duration than in the first two rounds, probably as a final attempt to make impact before the judges make their final decision [1].
Therefore, the first two rounds are the ones that last the longest in the battle.There seems to be a relationship between what the first dancer asks and what the second dancer answers, showing a type of "adaptation" to the battle.The temporal and sequential curve tends to be downward sloping in the confrontation.Factors such as fatigue, the dancer's adaptation to his opponent, resource management or even possible strategies may be the causes of such a tendency [24].
Our results show a comparison between the rounds of the first competitive period (2011-2016).In the first two rounds, the toprock is longer in duration, peaking at 9 s in the fifth round.The same occurs for the powermove, with a duration of 5 s in its first two rounds, peaking at 5 s in the sixth.The total round time decreases from rounds 1 and 2, conserving its values until the end, as if it were a conversation and everyone wanted to talk at the same volume [1, 24,29].
Except for rounds 3 and 4, a greater number of elements are performed in the answer than in the question, since going second in a round provides the dancer with previous information (the actions of the first dancer) so they are able to respond.Moreover, the answer concludes the battle and thus remains longer in the judge's mind [1, 24,25,29].The highest spin frequency (2.18 at round 6) coincides with the peak powermove frequency of the last round (3.61), confirming that both categories are in sync and tend to go hand in hand [1, 25,27].
The results tell us that the dancers in the second competitive period (2017-2021) have similar behavior to those of the first period, with the categories having a longer duration in the first two rounds, descending as the battle progresses, probably due to accumulated fatigue [14].As in the first competitive period, toprocks and powermoves stand out.The only differences are in drops, transitions and spins.Specifically, the frequency of drops and transitions is higher in the first two rounds, with a peak in transitions in the fifth round.The time of a spin coincides in the first two rounds (1.47 s), which is not coincidental, as the answer tends to match the question [24].On the one hand, these results could be indicative of which elements carry more weight in a battle and which elements tend to be repeated, modified or optimized, without losing sight of the context and the fundamental components of breaking [1, 24,28,29].
The comparison of the rounds between both competitive periods (2011-2016 vs 2017-2021) shows significant differences that confirm an evolution in approaches to dancing throughout the last decade.In general, the second competitive period (2017-2021) has higher values, with an increase in the content that the athlete has to cover, demonstrating that greater effort is required as the years advance.Thus, below, we will discuss some aspects that stand out in the second competitive period.Firstly, the duration of all the rounds is longer.In the dancer's second round, toprock time is longer, presumably because performing this element could help to achieve energy savings [1].In rounds 2, 3 and 4, drop time is higher, which shows higher content and greater variety of execution.Footwork time is higher in rounds 1, 2, 3 and 4, which indicates that this element has been gaining relevance.The first round comprises more elements, because it is one of the most important rounds, in which the dancer seeks to raise the bar for the answer [24,29].Toprock frequency is higher in rounds 1, 2, 5 and 6, and drop frequency is higher in the first two rounds, which indicates a change of direction towards more content, looking for changes in levels [25].Footwork is more frequent in the first round, again indicating greater relevance.The duration of an element is higher in rounds 3, 4 and 6, and the duration of footwork is higher in round 3.Both tend to provide a round with more volume, footwork being the core of breaking.The latter increased in frequency in the second period, prioritized more from the dancer's second round onwards [1,24].Clearly, all these data show a tendency towards a greater elaboration of the rounds.

Study limitations
We must take into account that there are factors within breaking that are very difficult or impossible to quantify and measure, such as those of a psychological nature or those that are not known and limit the study related to age, adrenaline, diet, supplementation, hours and method of training, hours of rest, nerves, quality of sleep and circadian hygiene, jetlag, reliability and training of judges, the athlete's habits, injuries or operations, etc. [1, 9,23,24,[29][30][31][32][33][34].
These subjective factors limit the study as they cannot be analyzed and measured yet there is little doubt that they influence the execution or direction of the battle.Furthermore, it should be taken into consideration that the data were extracted from the Red Bull BC One championships, which means the results should not be extrapolated to the entire breaking scene, as each dancer has a way and style of executing the movements, deciding what to prioritize.At the same time, it would be important to analyze if there are changes in approaches to dancing between men and women.

Practical applications
With the results of the study, we have developed a model of the temporal structure of the battle, taking into account the evolution of breaking over the last five years (see Table 8).

Conclusions
The average length of a breaking battle was 193 seconds, with rounds ranging from 29-37 s, thus concentrating a great deal of effort, explosiveness and wear and tear in short periods of time.Between rounds there is little rest time, which is equivalent to the opponent's performance time.
The powermove is still a mainstay in breaking and usually accompanied by a spin.As rounds progress, footwork gains relevance.Acrobatics play a much less relevant role than expected and blowups experienced a slight increase.Freezes are key to finishing rounds and are usually preceded by a powermove.
The first and last round of each dancer are the most important with greater use of powermoves, acrobatics or spins.The frequency and effectiveness of footwork has increased over the last five years.We find peaks of intensity in the last round of each dancer, showing that greater effort is made in the final phase of the battle.
There has been an evolution in approaches to dancing and battling.Breaking is evolving towards a more and more athletic and demanding standpoint.The effort that the athlete must make is increasingly greater and will therefore require better preparation to cope with the exhausting demands of an Olympic future.
We propose a model of temporal structure of the battle through which breaking professionals will be able to develop more precise and adequate training.

Table 2 . Descriptive analysis (total and by competitive periods), comparison of the competitive periods and size of effect of the sequential and temporal parameters of the breaking battles. Study variables Nor 2011-2021 2011-2016 2017-2021 Comparison Cohen's d or Hedges' g
* p < 0.05.

Table 3 . Descriptive analysis of the different phases of the competition and comparison among them (ANOVA or Kruskal-Wallis) of the sequential and temporal parameters of the breaking battles.
* p < 0.05.Nor = Normality; GTP = Global Temporal Parameters; GSP = Global Sequential Parameters; PTP = Partial Temporal Parameters.https://doi.org/10.1371/journal.pone.0293131.t003

Table 5 . Descriptive analysis of the rounds of the 2011-2016 competitive period and comparison between rounds (Kruskal-Wallis) of the sequential and temporal parameters of the breaking battles.
* p < 0.05.